I like to take refractometer readings when I am lautering and sparging to see if I hit a projected OG for 1st and 2nd runnings. Other than that I use a hydrometer (when I think about it). Quite frankly, I rarely take FG readings. I don't really care. I figure the yeast gave what it had to offer and I graciously and thankfully accept it.

I have 2 refractometers. I've never been able to get them to agree with each other or my hydrometer, so I don't use them. I can cool a hydrometer sample from boiling to 60F in less than 60 seconds so I don't really feel like I need a refractometer.

I'm on the fence with mine. Hygrometer works every time, and it's tough to beat it for precision and accuracy. Where it loses is convenience.

I calibrated my refractometer on two points, distilled water and a 1.080 (I think? was a while ago) sugar water solution. Sadly neither of the scales my refractometer read in were correct, however using the "refractometer tools" selection on Beersmith corrects for this error, and it now matches my hygrometer.

Where I've really run into issues is that I can't always get a repeatable reading. My concern is that this device could be just as temperature sensitive as the hygrometer, but without any way of measuring that temperature. Maybe other on here can explain.

I use the refractometer during the mash, always take original and final gravity readings with a hygrometer.

I finally spent some real money on a decent refractometer. I can't remember where I got mine now but it cost closer to $80 and is much more accurate than then cheap ones I tried off ebay for a couple years.

The ability to get a quick OG reading is invaluable for me since I have a lot going on during brewday, especially since I often have 2 brews going on at the same time.

one of the things you have to do is cool the sample first, I use a metal spoon and pull a few teaspoons out, blow on it and then put it on the sight glass, blow on that again and then close the lid and it sit a few seconds to stabilize.

I always use a hydrometer to check for FG because I want to be sure my reading is accurate.

I finally spent some real money on a decent refractometer. I can't remember where I got mine now but it cost closer to $80 and is much more accurate than then cheap ones I tried off ebay for a couple years.

The ability to get a quick OG reading is invaluable for me since I have a lot going on during brewday, especially since I often have 2 brews going on at the same time.

one of the things you have to do is cool the sample first, I use a metal spoon and pull a few teaspoons out, blow on it and then put it on the sight glass, blow on that again and then close the lid and it sit a few seconds to stabilize.

I always use a hydrometer to check for FG because I want to be sure my reading is accurate.

During the Winter at least, I take a sample with my brewing spoon and then pull a couple of cc's into a plastic pipet. I cap the end of the pipet with my finger and stick the bulb in a snow bank. Then I shake up the sample and add it to the platen.

I switched to a refractometer because I brew mostly small batches in which I would have to waste huge volumes of the batch taking a hydrometer reading. The testing jar takes what, six or eight ounces to get a hydrometer reading? On a one gallon batch taking an OG and FG reading is like 10% of the batch. I can take a refractometer reading with a few drops.

I expect that even adjusted with Sean Terrill's excellent calculator that the refractometer readings may be slightly off but a slightly inaccurate reading is better than no reading when I need one and I wouldn't take one on a small batch if it means sacrificing such a large percentage of the batch.

My primary use for my refractometer is for gauging the gravity of final runnings. In that case, it's going to be pretty accurate since the wort is nearly pure water and the instrument was calibrated to that and I know its correct. So its quick and accurate in that situation.

I guess I should kick myself for not having compared hydrometer and refractometer values in the past. So I'm not actually sure that my instruments agree at higher gravities. Guess I got some 'sperimentin' to do on the next brew.

A couple years ago, I mixed up a 1.040 solution with sugar and water, and compared the refractometer ($17 cheapo) and hydrometer. The hydrometer read 1.036 and the refractometer read 1.038. Since then, I have not used the hydrometer. All that cooling and excess wasted volume is too much a PITA.

But then, I'm not very worried about accuracy in either OG or FG. I'm just looking for comparisons to use in adjusting the next batch.